Place the peanut butter in a cold pan along with the brown sugar, garlic, ginger, chilli and 1 1/2 cups hot water. Now start the pan heating while you stir the mixture. It will look strange at first but simmer gently on a low heat, stirring all the time. Simmer until sauce reduces to required consistency. My favourite consistency is a little on the thick side so I cook it until a wooden spoon pulled through the mixture leaves a line in the pan. Then stir through the lime juice and soy sauce. Allow to cool before using on pizza. If sauce is too thick stir through extra lime juice until you get the consistency you desire.